Solutions for characterising samples by reading luminescent labels are known from prior art. A typical prior art solution has a light-emitting means for emitting excitation radiation having a first wavelength which is suitable for exciting a luminophore label, whereafter the excited luminophore material radiates emission radiation having a second wavelength characteristic to said luminophore material. The emission radiation is then detected by detection means. The excitation may be introduced also in the form of electric current or electric field, or a chemical reactant. In these cases the terms electroluminescence and chemiluminescence are used respectively.
One challenge related to prior art solutions is to distinguish the radiation used for excitation from the radiation emitted by the excited label and especially to detect only emission radiation. There are solutions that utilise monochromators to select and distinguish the wavelengths used for excitation radiation from the radiation emitted by luminophore labels. Another way is to employ time-resolved methods, as is described in US 2004/043502 A1, where the reader utilizes a pulsed excitation source and a time-gated detector with suitable control logic for measuring the intensity of the emission radiation.
Still another solution is described in US 2006/0055042, where a radiation source is located outside a measurement chamber where the sample is injected. The excitation radiation is injected through a semiconductor substrate into the internal cavity of the measurement chamber. For the detection of the luminescent radiation emitted by the luminescent substance, a plurality of radiation receivers are located on the semiconductor substrate with their detection side facing the internal cavity of the measurement chamber.
A further challenge related to prior art solutions is their inherently complicated structure and consequently high cost of manufacturing and operating, as well as the requirement of laboratory conditions. The use of monochromators, arrays of radiation receivers, scanning (confocal) detection, and/or time-gated detectors with suitable controlling logic tends to make the system complex and expensive and in addition vulnerable to malfunctions. The same is true concerning stepping motors and the like that move the sample holder to achieve reading of the wells. One should aim at developing a simple, robust, and low cost reader that is capable of sensitively recording and distinguishing the emission radiation from a plurality of sample wells or array spots, and that can be deployed even in harsh real-life environments.